• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.3
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• pp.159-164
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• 2024

Recent earthquakes in Korea, like Gyeongju and Pohang, have highlighted the need for accurate seismic hazard assessment. The lack of substantial ground motion data necessitates stochastic simulation methods, traditionally used with a simplistic point-source assumption. However, as earthquake magnitude increases, the influence of finite faults grows, demanding the adoption of finite faults in simulations for accurate ground motion estimates. We analyzed variations in simulated ground motions with and without the finite fault method for earthquakes with magnitude (Mw) ranging from 5.0 to 7.0, comparing pseudo-spectral acceleration. We also studied how slip distribution and hypocenter location affect simulations for a virtual earthquake that mimics the Gyeongju earthquake with Mw 5.4. Our findings reveal that finite fault effects become significant at magnitudes above Mw 5.8, particularly at high frequencies. Notably, near the hypocenter, the virtual earthquake's ground motion significantly changes using a finite fault model, especially with heterogeneous slip distribution. Therefore, applying finite fault models is crucial for simulating ground motions of large earthquakes (Mw ≥ 5.8 magnitude). Moreover, for accurate simulations of actual earthquakes with complex rupture processes having strong localized slips, incorporating finite faults is essential even for more minor earthquakes.

• Geomechanics and Engineering
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• v.19 no.3
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• pp.241-254
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• 2019

A finite element approach is presented to examine ground vibration characteristics under various moving loads in a homogeneous half-space. Four loading modes including single load, double load, four-load, and twenty-load were simulated in a finite element analysis to observe their influence on ground vibrations. Four load moving speeds of 60, 80, 100, and 120 m/s were adopted to investigate the influence of train speed to the ground vibrations. The results demonstrated that the loading mode in a finite element analysis is reliable for train-induced vibration simulations. Additionally, a three-dimensional finite element model (3D FEM) was developed to investigate the dynamic responses of a track-ballast-embankment-ground system subjected to moving loads induced by high-speed trains. Results showed that vibration attenuations and breaks exist in the simulated wave fronts transiting through different medium materials. These tendencies are a result of the difference in the Rayleigh wave speeds of the medium materials relative to the speed of the moving train. The vibration waves induced by train loading were greatly influenced by the weakening effect of sloping surfaces on the ballast and embankment. Moreover, these tendencies were significant when the vibration waves are at medium and high frequency levels. The vibration waves reflected by the sloping surface were trapped and dissipated within the track-ballast-embankment-ground system. Thus, the vibration amplitude outside the embankment was significantly reduced.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.451-458
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• 2002

This paper presents the prediction of deep excavation-induced ground surface movements using artificial neural network, which is of prime importance in the perspective of damage assessment of adjacent buildings. A finite element model, which can realistically replicate deep-excavation-induced ground movements was employed and validated against available large-scale model test results. The validated model was then used to perform a parametric study on deep excavations with emphasis on ground movements. Using the result of the finite element analysis, Artificial Neural Network(ANN) system is formed, which can be used in the prediction of deep exacavation-induced ground surface displacements. The developed ANN system can be effecting used for a first-order prediction of ground movements associated with deep-excavation.

• Coupled systems mechanics
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• v.1 no.1
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• pp.59-78
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• 2012

The available analytical methods of analysis for laterally loaded piles in level ground cannot be directly applied to such piles in sloping ground. With the commercially available software, the simulation of the appropriate field condition is a challenging task, and the results are subjective. Therefore, it becomes essential to understand the process of development of a user-framed numerical formulation, which may be used easily as per the specific site conditions without depending on other indirect methods of analysis as well as on the software. In the present study, a detailed three-dimensional finite element formulation is presented for the analysis of laterally loaded piles in sloping ground developing the 18 node triangular prism elements. An application of the numerical formulation has been illustrated for the pile located at the crest of the slope and for the pile located at some edge distance from the crest. The specific examples show that at any given depth, the displacement and bending moment increase with an increase in slope of the ground, whereas they decrease with increasing edge distance.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.69-76
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• 2003

This paper presents the prediction of deep excavation-induced ground surface movements using artifical neural network(ANN) technique, which is of prime importance in the perspective of damage assessment of adjacent buildings. A finite element model, which can realistically replicate deep excavation-induced ground movements was employed to perform a parametric study on deep excavations with emphasis on ground movements. The result of the finite element analysis formed a basis for the Arificial Neural Network(ANN) system development. It was shown that the developed ANN system can be effecting used for a first-order prediction of ground movements associated with deep-excavation.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.53-65
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• 2004

This paper presents the prediction of deep excavation-induced ground surface movements using artificial neural network(ANN) technique, which is of prime importance in the damage assessment of adjacent buildings. A finite element model, which can realistically replicate deep excavation-induced ground movements, was employed to perform a parametric study on deep excavations with emphasis on ground movements. The result of the finite element analysis formed a basis for the Artificial Neural Network(ANN) system development. It was shown that the developed ANN system can be effective for a first-order prediction of ground movements associated with deep-excavation.

• Structural Engineering and Mechanics
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• v.33 no.4
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• pp.407-428
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• 2009

The effects of the uniform and spatially varying ground motions on the stochastic response of fluid-structure interaction system during an earthquake are investigated by using the displacement based fluid finite elements in this paper. For this purpose, variable-number-nodes two-dimensional fluid finite elements based on the Lagrangian approach is programmed in FORTRAN language and incorporated into a general-purpose computer program SVEM, which is used for stochastic dynamic analysis of solid systems under spatially varying earthquake ground motion. The spatially varying earthquake ground motion model includes wave-passage, incoherence and site-response effects. The effect of the wave-passage is considered by using various wave velocities. The incoherence effect is examined by considering the Harichandran-Vanmarcke and Luco-Wong coherency models. Homogeneous medium and firm soil types are selected for considering the site-response effect where the foundation supports are constructed. A concrete gravity dam is selected for numerical example. The S16E component recorded at Pacoima dam during the San Fernando Earthquake in 1971 is used as a ground motion. Three different analysis cases are considered for spatially varying ground motion. Displacements, stresses and hydrodynamic pressures occurring on the upstream face of the dam are calculated for each case and compare with those of uniform ground motion. It is concluded that spatially varying earthquake ground motions have important effects on the stochastic response of fluid-structure interaction systems.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1170-1180
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• 2009

Recently this country has carried out the coast reclamation centering on the west and south coast for effective practical use of a country, considering purchase of materials and environmental problem, most reclaiming work is processing to spoil reclamation which is easy to secure the amount of materials. In case of weak ground that is formed by spoil reclamation like this, initial moisture content is high, as slurry state that is rarely revealed ground strength, compressibility and water permeability have been shown nonlinear change by compaction progress. Analysis of weak ground is unreasonable because the existing Terzaghi compaction theory analyzes compaction fixed number to regular invariable number for prediction of compaction state. This study computes the relation with void ratio-effective pressure and void ratio-finite transformation which is the most basic matter to predict finite strain compaction state of the south coast spoil, and analyze the basic feature to predict compaction feature of the south coast spoil reclaimed ground.

• Geomechanics and Engineering
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• v.34 no.4
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• pp.341-380
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• 2023

This study evaluates the seismic fragilities in fill slopes in South Korea through parametric finite element analyses that have been barely investigated thus far. We consider three slope geometries for a slope of height 10 m and three slope angles, and two soil types, namely frictional and frictionless, associated with two soil states, loose and dense for frictional soils and soft and stiff for frictionless soils. The input ground motions accounting for four site conditions in South Korea are obtained from one-dimensional site response analyses. By comparing the numerical modeling of slopes using PLAXIS^2D against the previous studies, we compiled suites of the maximum permanent slope displacement (D_max) against two ground motion parameters, namely, peak ground acceleration (PGA) and Arias Intensity (I_A). A probabilistic seismic demand model is adopted to compute the probabilities of exceeding three limit states (minor, moderate, and extensive). We propose multiple seismic fragility curves as functions of a single ground motion parameter and numerous seismic fragility surfaces as functions of two ground motion parameters. The results show that soil type, slope angle, and input ground motion influence these probabilities, and are expected to help regional authorities and engineers assess the seismic fragility of fill slopes in the road systems in South Korea.

• Structural Engineering and Mechanics
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• v.43 no.6
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• pp.835-845
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• 2012

This paper focuses on the stochastic response analysis of industrial masonry chimneys to surface blast-induced random ground motions by using a three dimensional finite element model. Underground blasts induce ground shocks on nearby structures. Depending on the distance between the explosion centre and the structure, masonry structures will be subjected to ground motions due to the surface explosions. Blast-induced random ground motions can be defined in terms of the power spectral density function and applied to each support point of the 3D finite element model of the industrial masonry system. In this paper, mainly a parametric study is conducted to estimate the effect of the blast-induced ground motions on the stochastic response of a chimney type masonry structure. With this purpose, different values of charge weight and distance from the charge centre are considered for the analyses of the chimney. The results of the study underline the remarkable effect of the surface blast-induced ground motions on the stochastic behaviour of industrial masonry type chimneys.